Means for producing oxids of nitrogen.



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APPLICATION FILED MAY 2, 1903.

3 SHEETS-SHEET 1.

MTNESS ES 'Nm 804,021. l v PATNTED NOV. 7, 1905.

E. MARQUARDT & H.;VIERTEL. v MEANS FOR PRDDUCING OXIDS 0F NITROGEN.

APPLIGATION FILED MAY 2, 1903.

3 SHEETS-SHEET 3.

JNVENTORS system of pipes forminga closed cycle. c rep- Qbodying our invention.

UNITED STATES PATENT loEEIoE.

,ERNST MARQUARDT, or scHoNEBERe, .NEAR BERLIN, AND HERMANN viERTEL, or oHARLo'TTENBURG, GERM-ANY.

MEANS FOR PRDIUCZING OXIDSA'O: NITROGEN.

Specification of Letters Patent.

l'Patented Nov. 71905.

, Application filed May 2, 1903. Serial No.' 155.364.

Tolfa/,ZZ whom -it may concern:

Beit known that we, ERNST MARQUARDT, chemist, residing at Schneberg, near Berlin,

f? Helmstrasse, and HERMANN VIERTEL, en-

gineer, .residing at Charlottenburg, near Berlin, 17 Goethestrasse, Germany, subjects of the German Emperor, have invented certain' new and useful Improvements in Means `for ProducingOxids of Nitrogen; and we do here- `by declare the following to be a full, clear,

and exact description of the invention, such as will enable others skilled in the art to which it appeitains to make and use the samen In producing oxids of nitrogen from mixtures of nitrogen and oxygen by. means of the electric arc the diiiiculty is encountered that only asmall part of the mixture takes part in the reaction and is transformed into oxids of nitrogen.l This difficulty hitherto formed a serious'drawback, because the product can not be easily and completely separated from amixture containing small quantities of it.

Our improved process consists in this, that a mixture of oxygen and nitrogen is forcedto perform a cycle continuously passi-ng through an electric arc o r discharge and thence to a cooling or absorbing apparatus, thence returning to the are, &c. rlhus a delinite quantity of 'gas is gradually enriched with -oxids of nitrogen until a concentration is reached at which every excess ot' product is retained in the cooling or absorbing apparatus. The uncondensedv part of the product continues to circulate with the mixture and in passing the arc is continuously enriched with fresh product which it yields in the condenser.

O .ur invention will now be described in connection with the accompanying drawings` and then particularly pointed out in the claims.

In the drawings, Figure l is a diagrammatic illustration of a simple form of apparatus em- Fig. 2 is a similar view of another modification. Fig. 3' is a detail view, partly in section., illustrating one form of electrode employed by us. Figs. 4, 5, and-6 are detail'views oi. other forms of electrodes which may be used.

Referring to Fig. lof the drawings, b is a resents electrodes between which an electric discharge or arc is supposed to be maintained.

. may

asa mixture of ice and salt or. solid carbonio acid. e is a condenserr in which the formed product collects and from whichA it can. be drawn off by means of a spigot f. At a is indicated a vessel :containing the raw material, and g is a pipe connecting the vessel a with I the system Z).

Referring to Fig. 2, b is the system of pipes forminga closed cycle. c2 represents the electrodes between which the electric discharge or arcisproduced. ZZ2indicatecoolingdevices, each having an inlet (Z3 and an outlet aZ4 for the supply of a suitable cooling medium. e is a condenser in which the product is collected and from which it may be drawn off by the spigot f. At a' is indicated a reservoir for the rawI material-for example, oxygen or air and oxygen-.this reservoir being in the Jform of a floating gas-bell, from which a pipe g leads to a suitable drying apparatus Z, having a pipe Z2, by means of which sulfuric acid i be supplied to the drier to absorb the moisture from the gas, the weakened acid being drawn off when desired through the spigot Z3. The drying apparatus is connected by a pipe g2 with a suitable `pump or compressor,

pipe g is connected a pipe g5, leading from 2L -suitable supply ofraw material. The pipe g5 is provided .with a valve gl. By closing the valve g4 in the pipe g and opening the valve ge a supply .of ra'w material may be forced into the gas-'bell a', after which the valve g by the supply of raw material under pressure in the l closed-pipe system b as required-by the material being deprived of its moisture on its way through the drier Z.

At y' is indicated a rotary blower or pump, which may he used to circulate the material in the closed-pipe system b'; but, preferably, a heating device is applied near the bottom of one side ot' the closed-pipe system in order to maintain such a circulation. For example, as shown in the'drawings, the pipe system may be provided withja heating-jacket a', having an inlet 2V and an outlet c" for the supply of steam.

gas-bell a may be fed to the.

as indicated at if', and the latter is connected Y by a pipe'g3 with the closed-pipe system Z'. In the pipe g is located a valve g4, and to saidmay be closed and the valve g4 opened, wherepump 7c' at Ithe desired' pressure, the said raw `subjected to condensation orvabsorptidniwhich f contains a considerably higher percentage of nitrogen tetroxidv l(NzOi or NO2) thanl would be economically possible with. other methods of working. Moreover, -'w.e avoid thevery considerable losses which are lthe consequence of the usual method of procedure,.whichcon sists in compressing'and cooling a definiteA quantity of gas mixture after treatment in the arc for the purpose of condensingthe'obtained product and -then allowing the residue to escape.` *l

A further advantageof the process conslsts in this, that it is thereby `possible directly to obtain concentrated and pure products. For instance, we have 'succeededin obtaining liquid and solid vnitrogen tetroxid by mixing the gases required for'the'formation of this product, notabiy nitrogen and oxygen,- in stoichiometrical proportions and allowing them Vto ci rculate between anj electric discharge'and a condenser at a pressure of from two/to ten atmospheres. When a-higher 4pressure is chosen,

the temperatureof thecondenser need not be as low. `When the pressure in the apparatus is equal to the' atmospheric pressure, the condensermust be cooled to Iatemperature as low as 70O centigrade or even still lower.

A sulicient automatic circulation'can be maintained-by the ditference'of temperature between the arc and the condenser if the former is arranged so as to allow the warmed gas mixture to rise -up and if `the cooling'part of the circuit be directed downward. For this purpose the arcis placed at a low position in the rising branchofl the circuit.. In some l cases weV prefer to produce vthe necessary circulation by means of a separate` source of heat-applied to the'lower portion of the cycle,. as indicated by the heater shown at z', Fig. 2. By regulating the source of heat the-speed of circulation can then also be regulated within certain limits. However,v the circulation can also bemaintained and regulated by means o f a special apparatus, such as a ventilator or a pump, as indicated at j, Fig. 2. Howe-ver', this method of regulating the'speed of circulation hasthe disadvantage of` being' complicated, and, moreover, lthe regulator or pump is seriouslyvattacked bythe oxids-of nitrogen if special precautions are not provided. l

The system forming the cycle is kept inconnectionwith a vessel containing oxygen and nitrogen. As oxygen andnitrogenare used up fre'sh gas is from time to time introduced .it the proper pressure.

Instead of mixing the-required gases in stoichimetrical proportions and then introducing them it is also possible to introduce large percentage of oxygen separately as each constituent maybe required by the process. 'By spectroscopic observation or by measuring thecounterelectromotive-force of the arc or by-testing a s'rnalrq uantity of the gas mixture it can be found whether oxygen or nitrogen should be added inorder to maintain the reaction inthe most advantageous state. However, `as a rule no more gas should be introratus in the shape of oxids of-nitrogen.

When mixtures areA employed which are not portion ot' their combining weights for nitro- `gen tetroxid, but rathencontain an'exce'ss of nitrogen-as, for instance, atmospheric air without an addition ofv pure oxygen-it will be evident thatthe closed cycle can only be maintained' until the mixture is too much enriched-with excessive nitrogen. this process the nitrogen must be allowed to escape and must be replaced by'ay mixture richer in oxygen. The smaller Athe excess of nitrogen ischosen the longer it will be possible to maintain the circulation and the more Vadvantageus'the process will become. `I`he most advantageous proportions of the mixture employed will therefore practically depend upon the market price of oxygen or the mixture of oxygen andnitrogen and` on the priceof the obtained product.

'We prefer to employ amixture containing oxygen and nitrogen `in the same'proportions as does'nitr'ogen tetroxid or the mixtures ob- 'tained by condensing atmospheric air containing about fifty per cent; nitrogen and fifty per cent. oxygen. v.

In any case the whole process is veryvsmple. `Continuous working is possible, which requires only very little supervision, and the losses ot' energy and of material are reduced to a minimum. Instead ot' condensation by means of cooling suitable absorbing-bodies can be introduced into the cycle according' to the nature of the products sought for, such as cold water, nitric acid, caustic soda, organic air and oxygen or air and gases containing a 'composed of nitrogen and oxygen in the pro-v duced than is condensed in the cooling appa- Then also in IOO bodies absorbing oxids of nitrogen, and such The voltage of the'currents We employ dif- 'fers according to the products we wish to obtain. If we desire' to produce as cheaply as possible nitrates or compounds containing oxids of nitrogen, we employ low electromotivev forces of thirty t9 one hundred Volts. VVelthen use i'n the apparatus cheap mixtures of nitrogen and oxygen, such as atmospheric a1r under a pressure of about one to two atmospheres. O course 1n using such a mix- Y Having now particularly described and a's.V certained the nature of our said invention and in what manner the same istobe performed, we declare that whatwe claim is` 1. Means for producing oxids of nitrogen froma mixture vof oxygen and nitrogen, whichv means consists inthe combination, .with a system of pipes forming a closed cycle, of an electric-discharge device arramgedv withinsaid system, mean'sforseparating the formed product, a vessel* terial', 'and means for introducing under pressure greater than atmospheric fresh material from said/Vessel to saidsystem.

2. In an 'apparatus' ofthe class described, the combination, with a system oi' pipes forming aclosed cycle, of an electric-discharge device arranged Within said system, and means external to the closed system, connected there `with and arranged to supply fresh materialto said system', under a' pressure greater than atmospheric.

3. Means for from a mixture Voi oxygen and nitrogen, which 3. heat independent of theelectri'cfdischarge de- *,pairpf electrodescontainingmetal-'compounds 4o the formed means consists in the combination, with a system of pipes forming a closed cycle, of agri electric-discharge'device arranged'in said system, means forseparatng the formed product, a vessel adapted to contain fresh ravvv material and connected to saidA system. and a source of viceand arranged to heata` lo'wer portion of thesaid system, whereby 'a -maintained in said system. 35 i 4. Meansfor'produ'cing oxfids of nitrogen from a mixtureof oxygen andnitrogen, which -means consistsin the combination, with a system of pipes v for-ming a closed cycle, of .a

arranged in-said system, means for separating product, a vessel formedl product, a

means forseparating the raw material, and

vessel arranged to contain adapted to contain fresh raw ma.

'.comp

producing oxids of nitrogen Aof circulation is l containing fresh ravv material and connected to said-system,-

means for introducing the raw material into whichmeans consist'in the combination, withv asystem of pipes,'of mechanism for producing.'

an electric arc in rising electrodes ,containing carbon, the points of which. are with the gaseous mixture by means of asleeve ofrefractory An ia .terial,:means for` separating protected against contact said system, said mechanism the formed product, aA Vessel for containing the/raw material, 'and jineans for introducing the i'aw material into the saidfsystem,fsub

stan'tially as and `for the purpose described.

7. An apparatus foi'l the production of oxids of nitrogen provided With electrodes'containing calcium luorid., 8`. .An apparatus for the production of oXids nitrogen having electrodes containing carbon Vand calcium iiuorid.

9. -Anapparatus for the'piroduction of oxids of nitrogen havingr electrodes consisti-ng'essen--' tially of carbo\nand calcium Huorid.

In testimony Whereowe have aiixed our signatures to this specification in the presence of two Witnesses.

' ERNST MARQUARDT.

'HERMANN VIERTEL.

VVitnes'ses: WOLDEMAR Ham, 'HENRY HASPER; 

